Antenna Effect for Enhanced Near-Infrared Luminescence in Lanthanide-Doped Nanoparticles: Mechanisms, Strategies, and Applications.

Near-infrared (NIR) luminescent materials hold significance in various sectors, including healthcare, astronomy, environmental monitoring, and information encryption. As a unique subset, lanthanide-doped nanoparticles (Ln NPs) are particularly key NIR materials due to their unique spectral properties, but their luminescence efficiency is hampered by inherently weak light absorption via forbidden f-f transitions. "Antenna effect" strategy has emerged as a crucial paradigm for overcoming the intrinsic absorption limitations. By employing sensitizers like organic dyes, quantum dots, or transition metal ions to capture light and transfer energy to lanthanides activators, this approach significantly enhances emission intensity of Ln NPs. Consequently, this enhanced performance directly broadens their application scope, paving the way for advanced applications such as high signal-to-noise ratio NIR imaging, in vivo sensing, NIR illumination and NIR multichannel anti-counterfeiting. This perspective analyzes these three antenna systems, comparing their mechanisms, performance, and limitations. Finally, persistent challenges and emerging opportunities is discussed focusing on optimizing nanoparticle brightness, enhancing long-term stability under demanding conditions, and expanding spectral versatility beyond conventional NIR windows. These advancements promise to drive fundamental biological discovery, accelerate clinical translation through multichannel in vivo imaging and precision-guided therapy, and enable advanced information security systems for next-generation technologies.